One general division among pneumatic tires for vehicles can be made between off-the-road tires and over-the-road tires. Off-the-road tires are conventionally used on construction vehicles and the like and methods and apparatus for the retreading, renewing or rebuilding of such tires have been developed as described in the aforementioned parent application. The same difficulties and deficiencies which have led to the development of techniques which have replaced mold curing for off-the-road tires are factors in the retreading, renewing or rebuilding of over-the-road tires and particularly of truck tires and the like. For the reasons generally outlined in those prior disclosures which relate to retreading, renewing and rebuilding without reliance upon mold curing, effort has been directed toward the development of such techniques for truck tires and the like.
One example of apparatus and methods which have been so developed is to be found in Barwell U.S. Pat. No. 3,808,076 which describes a method and apparatus for applying tread material in which tread material is extruded under pressure as a tread pattern is formed in the material. While tires retreaded, renewed or rebuilt in accordance with the Barwell disclosure have operated satisfactorily, the range of tread designs which may be achieved by the method and apparatus there disclosed is somewhat restricted and is more restricted than is desirable to users of such tires.
Prior to Barwell disclosure, it has been disclosed that tread designs may be formed in over-the-road tires by grooving techniques bearing some similarities to the grooving techniques described in the aforementioned parent application. However, such grooving techniques have been highly reliant upon the manual skill of an individual operator and have, even so, been somewhat restricted in the range of tread patterns which could be readily and economically produced.